The aim of this project is to develop an automated hearing threshold estimation system using cortical auditory long-latency evoked responses (LLR) analyzed objectively in a steady-state condition. Test methods that dominate clinical practice today, such as auditory brainstem response (ABR) and auditory steady state response (ASSR), permit only indirect inferences about hearing sensitivity and cannot provide a comprehensive view of the auditory pathway, as can be achieved with cortical responses. Previously, maturation and level-of-arousal issues, as well as lack of comfort by clinical audiologists in the interpretation of LLR results have limited their widespread clinical implementation. The investigators have demonstrated in their previous work and in a number of recent publications that an objective analysis approach can be successfully applied to the LLR ? defined as the Auditory Steady State Long Latency Responses (ASSLLR) -- using modulation rates below 20 Hz. The work to date has demonstrated success in adults, children and infants with a planned focus for this application on this youngest group, as they cannot be tested by conventional audiometry and because they present the greatest challenges for cortical responses. The specific aims of this Phase II project are, as follows: 1) Optimization of the ASSLLR acquisition system to improve data and spectral analysis resolution and incorporation of response analysis and detection algorithms onto the system platform currently manufactured and marketed by Intelligent Hearing Systems, 2) Refinement of algorithm and analysis tools for response detection and noise reduction, 3) Evaluation of the system for data acquisition in subjects with normal hearing (n=20) and in children and adults with known sensorineural and conductive hearing losses (n=50) compared to behavioral thresholds, 4) Evaluation of the system for data acquisition and analysis in newborns and young infants (n=80) compared to ABR with special attention to participant state. Work will also involve development of test protocols and reference datasets based on the outcomes of Specific Aims 3 & 4 and demonstration that responses can be acquired with supra-threshold speech stimuli as well. The successful completion of this work will result in a clinical tool that will provide methods for objective evaluation of the auditory system that includes the cortical level.